Small 56 degrees BB frame

[noblecycle]

Dear frame lug builders,

I will braze a small 52cm frame, OS, 5 degrees slopping.
It's my first small frame and until now I had a bb angle of 59 minimum. But for this one, I need to reach a 56 ! (not mentionning the 58 down ht lug...)
here is the drawing :

smallframelugs.jpg

I ll be happy to receive any comments about this,

Thanks,
Nicolas

[suhacycles]

Interesting that you should ask about this... Ceeway is offering a lugged BB shell with 57/64/7 deg angles but in OOS size. According to Peter only the non-stainless is available right now:

http://www.framebuilding.com/NEWPART...B%20Shells.htm

[zetroc]

Perfect application for a nice fillet braze!

[Curt Goodrich]

I can't see in the drawing what the bb drop is nor the stem length. First thought is if you don't feel comfortable cranking the shell to work to those numbers you may be able to finesse things a bit. Like if the drop is a lot like 80mm perhaps you could raise it by 5mm. That will help a little. If you designed around a long-ish stem for a frame of this size perhaps you can add a cm to the top tube and size down the stem a cm. That too can help a little. Still little frames can be a challenge due to the issue you're seeing. Personally if I'm happy with the frame design I've cranked bb shells to fit without a lot of fuss. Good luck.

[noblecycle]

Ceeway is offering a lugged BB shell with 57/64/7 deg angles but in OOS size

Yes, I had seen this, but I can't go OOS

Perfect application for a nice fillet braze!

I'm not experienced enough on fillet for the moment, but yes...this is the solution !

I can't see in the drawing what the bb drop is nor the stem length. First thought is if you don't feel comfortable cranking the shell to work to those numbers you may be able to finesse things a bit. Like if the drop is a lot like 80mm perhaps you could raise it by 5mm. That will help a little. If you designed around a long-ish stem for a frame of this size perhaps you can add a cm to the top tube and size down the stem a cm. That too can help a little. Still little frames can be a challenge due to the issue you're seeing. Personally if I'm happy with the frame design I've cranked bb shells to fit without a lot of fuss. Good luck.

Thanks Curt, after changing stem from 100 to 90 and bb drop from 70 to 65 and adding the cm to de tt, here is the result :

smallframelugs65bb.jpg

It s definitely ok for the ht down lug and it s better for the BB ST/DT with 57.5 degrees. But it transfers the problem on the ST/CS with a big 66 degrees.
Did you crank the bb up to 3 or 4 degrees ? did you simply use plain tubes ?

Thanks again for helping

[Curt Goodrich]

Yes, I had seen this, but I can't go OOS


I'm not experienced enough on fillet for the moment, but yes...this is the solution !



Thanks Curt, after changing stem from 100 to 90 and bb drop from 70 to 65 and adding the cm to de tt, here is the result :

smallframelugs65bb.jpg

It s definitely ok for the ht down lug and it s better for the BB ST/DT with 57.5 degrees. But it transfers the problem on the ST/CS with a big 66 degrees.
Did you crank the bb up to 3 or 4 degrees ? did you simply use plain tubes ?

Thanks again for helping

I've definitely made bb shells work in that configuration. A combination of bending and grinding will get you there. Is the seat angle really 75? That seems too steep. Is the head angle really 73? That seems too steep for a bike of this size too. Or am I misunderstanding your drawing?

[noblecycle]

I've definitely made bb shells work in that configuration. A combination of bending and grinding will get you there. Is the seat angle really 75? That seems too steep. Is the head angle really 73? That seems too steep for a bike of this size too. Or am I misunderstanding your drawing?

You're right.
The 73 ht will change. The 75 st is a specific need of the customer, actually using 0 offset saddle (on a 74.5) and want to have more choice on seat post.
Interested about any suggestions...